FR2589554A1 - DETACHABLE MONOBLOCK DEVICE FOR BLOCKING THE PASSAGE BETWEEN TUBES IN A NUCLEAR REACTOR VAPOR GENERATOR - Google Patents

Abstract

REMOVABLE MONOBLOCK DEVICE FOR BLOCKING THE PASSAGE BETWEEN TUBES IN A NUCLEAR REACTOR STEAM GENERATOR. THIS DEVICE 40 INCLUDES AN L-SHAPED PROFILE 50 FIXED TO THE CLOSED END OF A CYLINDRICAL SLEEVE 41. THE OPEN END OF SLEEVE 41 INCLUDES AN ANNULAR RING 42 FOR RETENTION TO MOUNT IN THE WALL OF THE TANK GENERATOR AT THE FISTHOLE ENTRY. THE DIMENSIONS OF THE LOCKING DEVICE 40 ALLOW IT TO BE INSERTED THROUGH THE FISTHOLE AND INTO THE PASSAGE BETWEEN TUBES TO A POSITION OF USE IN WHICH THE FAREST BRANCH 52 OF THE L-PROFILE 50 IS PERPENDICULAR TO THE TUBULAR PLATE. THE ASSEMBLY SLEEVE 41 IS THEN HELD IN PLACE IN THE PUNCH HOLE BY LOCKING SCREWS WHICH GO THROUGH OPENINGS 44 SHAPED IN THE SLEEVE 41. APPLICATIONS: IN PARTICULAR TO ADJUSTING THE FLOW OF THE WATER IN THE INSIDE OF THE BEAM OF TUBES OF A HEAT EXCHANGER.

Description

Removable monobloc device for blocking the passage between tubes in

  a nuclear reactor steam generator.

  The present invention relates generally to the sample tanks

  heat exchangers, such as nuclear reactor steam generator vessels, and particularly relates to means for controlling the flow of the heat exchange fluid outside a

  beam of heat exchange tubes.

  A conventional nuclear reactor steam generator includes a vertically disposed shell or vessel and a plurality of inverted U-tubes positioned within the shell to

  form a bundle of tubes. Each tube comprises two vertical parts

  the elongations connected at the upper end by a bent part,

  so that the vertical parts of each tube overlap a step-

  wise central through the bundle of tubes. A tube plate

  carries the vertical parts of the tubes at their lower ends.

  The vertical parts of the tubes, on one side of the central passage,

  with the inlet portion of the primary fluid while the vertical portions of the tubes located on the other side of the central passage communicate with an outlet compartment of the primary fluid under the tube plate. The steam generator also comprises a cylindrical sheet metal jacket disposed between the bundle of tubes and the ferrule so as to form an annular chamber with the interior of the

the ferrule.

  The primary fluid that has warmed up while circulating in the

  reactor core, enters the steam generator through the

  The inlet fluid of the primary fluid is conveyed in the bundle of tubes and exits through the outlet compartment of the primary fluid. At the same time, a secondary fluid or feed water circulates around the tubes, above the tube plate, in order to carry out a heat transfer with the outside of the tubes, so that a portion of the feed water is transformed. steam which is then circulated in a conventional generator. More particularly, the water

  food goes down into the annular chamber along the outer face.

  top of the liner to the tube plate, and then back up

  among the tubes inside the shirt.

  Food water contains particulate matter, mainly

  in the form of iron oxides and cuprous compounds, as well as traces of other metals, which tend to deposit from the feed water on the tube plate in the zones thereof.

  o the flow velocity of the fluid from one end of the tubular plate

  to the other is insufficient to prevent sludge deposition. This

  deposition is harmful because it creates accumulations of sludge

  kill corrosion agent concentration sites along the walls of the tubes and result in corrosion of the tubes. Because there are no tubes in the central passage, it is desirable to minimize flow along this central passageway in order to increase the lateral flow through the tube bundle, by thereby reducing the dimensions of the zone of the tube plate in which the lateral flow velocity is insufficient to

prevent the deposit of sludge.

  For this purpose, there are provided in some steam generator vessels blocks incorporated in the central passage between tubes for

  prevent the flow of food water along these tubes. How-

  However, these built-in tube blocks have been provided only in relatively recently constructed nuclear reactor steam generators. In the case of older steam generator tanks, they had to be modified by equipping them with removable blocks placed in the passage between tubes. These blocks had to be introduced through the available punch holes of the tank wall at a low height above the tube plate, the punch holes typically being in alignment with the central passage. The blocks of the passage between tubes are introduced in sections sufficiently small to be able to pass into the hand hole, the blocks having fasteners provided to fit cradles mounted on the tube plate, the parts being introduced by a cutout provided in the shirt. Separate half-lids are then put in place to close the cutout of the liner, these half-lids being introduced

  in grooves of the blocks so as to prevent any vertical movement

  tical of these. The half-lids are then attached to a man-

  chon housed in the hand hole and they are held in place by fixing screws. The complete assembly is then sealed by means of

the cover of the hand-hole.

  This arrangement ensures effective blocking of the passage between tubes,

  but it is extremely time-consuming and costly to set up and demonstrate

  b. Whenever it is desired to remove sludge or perform any other maintenance operation, such as searching for and removing foreign matter, the block assembly must be removed by removing the sleeve and the separated half-lids piece by piece. while pulling up

  then the blocks out of their grooves and away from the passage.

  This leads to considerable radiation exposure of the operator. In

  In addition, there is an important possibility of leaving spare parts

  in the generator. We must carry out with great care the

  set up and dismounting so as not to damage the tubes.

  The present invention provides an improved device for blocking the passage between tubes in a heat exchanger tank, this locking device avoiding the disadvantages of the following devices

  the prior art while offering additional advantages of

tioning.

  In particular, the present invention provides a device for blocking the passage between tubes of the type mentioned, this device being simple, economical and easy to assemble in and remove from the tank of the heat exchanger because it is in a monobloc form and, therefore, without any risk of loss of parts within the

steam generator.

  In its general form, the present invention resides in a removable device for blocking the flow of the heat exchange fluid in a central free passage through the bundle of tubes and above the tubular plate of a tank. heat exchanger of a steam generator having a hand-hole in the alignment of the central passage, which device is characterized in that it comprises a blocking part which can be introduced by the hand-hole into the central passage , and a mounting portion connected to the locking portion and secured in the mounted handhole, said mounting portion forming a one-piece assembly movable between a withdrawal position, located completely outside the tank of the heat exchanger, and a use position in which the mounting portion is in the mounted position, while the locking portion is oriented in the locking position in the central passage so

  to prevent the flow of fluid along this central passage.

  - The description below relates to a removable device of

  blocking the flow of the heat exchange fluid in the free central passage through a bundle of tubes, above the tube plate, in a heat exchanger vessel having a punched hole in the alignment of the central passage, which device comprises: a blocking part which can be inserted by the hand-hole into the central passage, and a mounting part connected to the locking part and fixed in the hand-hole in the assembled position, this part of blocking and this mounting part forming a movable monoblock assembly between a withdrawal position, located completely outside the heat exchanger tank, and a use position in which the mounting part is in the mounted position , while the locking portion is oriented in the locking position in the central passage to prevent the flow of fluid therethrough

central passage.

  The present invention has certain novel features and a combination of parts which will be fully described hereinafter. The present invention will be well understood on reading the

  following description with reference to the accompanying drawings, in

  which: - Figure 1 is a partial view, in vertical section, of a

  nuclear reactor steam generator vessel, illustrating

  Positive blocking of the passage between tubes in accordance with a

  according to the prior art; FIG. 2 is a partial view on a larger scale, in

  horizontal section along the section plane 2-2 of FIG.

  the blocking devices for the passage between tubes

prior art;

2S89554

  FIG. 3 is a partial view, in vertical section, of

  the sectional plane 3-3 of FIG. 2; FIG. 4 is a perspective view of a tube passage blocking device constructed in accordance with the present invention and having the features of the present invention; FIG. 5 is a front view, on a slightly larger scale, of the device for blocking the passage between the tubes of FIG. 4; - Figure 6 is a vertical sectional view along the sectional plane 6-6 of Figure 5; FIG. 7 is a partial view on a larger scale, in vertical section, of part of the steam generator vessel of the

  FIG. 1, illustrating the initial stage of assembly of the locking device

  cage of the passage between tubes of FIG. 4; - Figure 8 is a view similar to that of Figure 7, illustrating the locking device of the passage between tubes in the mounted position;

  FIG. 9 is a partial view, in horizontal section, of

  the section plane 9-9 of FIG. 8; and

  FIG. 10 is a partial view, in vertical section, of

  the cutting plane 10-10 of FIG. 9.

  Reference is made to FIGS. 1 and 2 which illustrate a nuclear reactor steam generator vessel, generally designated by numeral 20, which comprises an elongate and generally cylindrical side wall 21. A circular tubular plate 22 is placed across of the tank 20 and closes the latter in the vicinity of

  its lower end. The vessel 20 has a generally lower end

  Hemispherical 23 which extends under the tube plate 22 and which is connected thereto by a central upright 24. A partition (not shown) separates the region between the tube plate 22 and

  the lower end 23 into two chambers or compartments 25 comprising

  both each tubing 26 (one of which is shown) and a hole

  Man 27 (one of which is shown). Tubings 26 are respectively

  connected by pipes (not shown) to an associated nuclear reactor. The manholes 27 are closed by removable covers to allow access to the compartments 25. In the side wall 21, at a slight distance above the tube plate 22, are formed two or more punches 28 provided removable covers (not shown) to allow access to the interior of the tank 20, above the tube plate 22. For the purposes of the present invention, each handhole 28 has at its end

  outer one or more counterbores 29 (see FIGS. 7 to 9).

  In the tank 20, above the tube plate 22, is

  placed a tube bundle 30 comprising a plurality of inverted U tubes 31 whose branches overlap a central passage 32 between tubes, this passage extending diametrically across the tube plate 22, parallel to the axis of at least two of The two branches of each tube 31 respectively communicate with the compartments 25 through the openings (not shown) of the tube plate 22. A cylindrical jacket 33 surrounds the bundle 30 of tubes coaxially with the side wall 21 and it is spaced a slight distance internally to the inner surface of this wall. The liner 33 has a cut-out 34 of its lower edge, in the vicinity and in alignment with one of the fist holes 28. A bleed pipe 35 may be provided along the central passage 32 between tubes, immediately above tubular plate

22 (see FIGS. 7 and 10).

  In operation, the primary fluid from the core of the reaction

  The driver enters the compartment 25 which is the entrance compartment, is a vehicle in the tube bundle 30 and exits through the compartments 25 which constitutes the exit compartment, then returns to the reactor core. The secondary food water circulates in the tank 20, above the tube plate 22, in order to achieve

  heat exchange with the bundle 30 of tubes. More specifically

  -men - .. Gau..imentaire-descends - years-the-annular space formed between the side wall 21 of the tank and the jacket 33, collides with the tube plate 22 and then goes up through the beam 30 of tubes, the

all in a well known way.

  The lateral flow velocity of the food water of an ex-

25895S4

  the end of the tubular plate 22 to the other, may vary in

  22. If it is sufficient, this flow rate can prevent the accumulation of sludge due to deposition of sediment from the feed water. Thus, to maximize the lateral flow velocity in the zones of the tube bundle, it is desirable to minimize the flow velocity in the central passage 32 between tubes, where there are no tubes. . For this purpose, on the previous tanks of steam generators, blocking devices have been used in the central passage 32 between tubes in order to prevent the flow of drinking water along this passage. In an assembly of this type according to the prior art, blocks 36 are mounted in the central passage 32 between tubes, these blocks being held laterally in place by a cradle 37 mounted on the tube plate 22 and being held vertically in place by separate half-lids 38 introduced into grooves of one of the

  blocks 36 mounted in the passage between tubes. These separate half-lids

  res 38 are fixed by welding or bolting to a tubular sleeve

  re 39 which is housed in the associated handhole 28 and is held in place by means of fixing screws. This assembly in several parts is characterized by a relatively difficult and long implementation,

  requiring considerable radiation exposure of the operator.

  In addition, to carry out certain maintenance operations such as the sludge evacuation and the search for and the removal of foreign bodies, this device must be dismantled according to the prior art of blocking the passage between tubes in order to allow access to the central passage 32 between tubes and the space formed between the liner 33 and the side wall 21 of the tank. This requires the removal of the sleeve 39 and separate half-covers 38, and the clearance of the blocks 36 mounted in the passage between tubes so that they can be spaced from the path along the central passage 32 between tubes. This dismantling represents a very long process and results in a

  significant radiation exposure of the operator.

  Reference will now be made in particular to FIGS. 4 to 10.

  The present invention provides an improved device for blocking the

  central passage between tubes, generally identified by the reference

  numerical resistance 40 and characterized by a single piece construction, simple and economical, so that it can be easily set up and deposited as a set. More particularly, the locking device 40 comprises a tubular sleeve 41 which is similar to the sleeve 39 according to the prior art, but it is equipped at its outer end with an annular retaining ring 42 projecting radially outwardly, the inner end of the sleeve 41 being closed by

  a flat circular lid 43 which is fixed in place by welding.

  Three threaded openings 44 are formed radially through the sleeve 41, the axes of these openings being in a common plane substantially perpendicular to the axis of the sleeve 41. Three threaded bosses 45, designed to receive respectively locking screws 46, are fixed on the inner surface of the sleeve 41 and communicate respectively with the openings 44. Lugs 47 for security threads may also be provided on the inner surface of the tubular sleeve 41 to cooperate with security threads (not

  represented) in order to maintain the screws 46.

  A blocking element 50, integral with the flat lid 43 and having as a whole the shape of an L, comprises a rectangular flat branch 51 of mounting fixed by welding to the flat lid 43, and a flat rectangular locking arm 52 disposed approximately close perpendicular to the mounting branch 51. It is preferable to provide a plate 53 forming a gusset between the mounting branch 51 and the flat cover 43, and a plate 54 forming a gusset between the branch 51 of

  assembly and the locking branch 52, all in order to provide rigidity

construction.

  The locking element 50 has a width slightly smaller than that of the central passage 32 between tubes, so as to be able to substantially block the passage 32 between the tubes in the lateral direction, and it has a length slightly less than the vertical distance between the axis

  hand hole 28 and the tube plate 22.

  In practice, to set up the blocking device 40, the lid of the hand-hole is removed and the end farthest from the blocking branch 52 is introduced through the hand-hole 28,

  as shown in FIG. 7, this locking branch 52 is prolonged

  Geant through the cutout 34 of the jacket 33 and along the central passage 32 between tubes. When the blocking branch 52 is approximately fully inserted into the handhole 28, the blocking device 90 is rotated counterclockwise in the direction of FIG. 7 , while continuing its introduction, so as to move the mounting leg 51 through the hand-hole 28 and to introduce the sleeve 41 into the hand-hole 28, the depth of introduction being limited

  by the embouchement of the retaining ring 42 in one of the counter

  bores 29 of the handhole 28, as illustrated in FIGS. 8 to 10.

  When the blocking device 40 is thus placed in its mounting position, its blocking branch 52 is arranged vertically in a locking orientation, perpendicularly to the tubular plate 22 and to the axis of the central passage 32 between tubes. In this mounting position, the farthest end or lower end of the blocking leg 52 is at a slight distance above the tube plate 22, so as to allow the passage of the purge pipe and the cradle. 37 below this branch. As best shown in FIGS. 8 and 10, in this mounting position, the inner end of the sleeve 41 extends through the

  cutout 34 formed in the shirt 33.

  When the blocking device 40 has thus been placed in its mounting position, it is held in this position by screwing the locking screws 46 radially outwards in order to bring them into contact with the internal surface of the hand-hole 28, in order to securely lock the sleeve 41 in place. Because of the scope of the

  retaining ring 42 in the counter-bore 29, no part of the arrangement

  Blocking device 40 does not protrude outside the handhole 28, thereby facilitating the placement of the cover (not shown) of the handhole 28 thereby closing the latter in a fluid-tight manner. It should be appreciated that, when it is desired to disassemble the blocking device 40, it is sufficient to remove the cover from the hand-hole and to loosen the blocking screws 46, which makes it possible to remove from the tank 20 the whole of the blocking device 40. locking device 40, in the form of a one-piece assembly, by reversing the movements described above and by rotating the locking device 40 of about 90 'in the

  sense of clockwise rotation to allow the pass-

  the locking member 50 is engaged in the handhole 28.

  This simple installation and disassembly of a monobloc device by an operation that is carried out substantially in a single time, can be done quickly and easily with a minimum of radiation exposure of the operator. In addition, a significant advantage of the present invention lies in the fact that the locking device 40 can be set up easily and accurately, by running a minimum risk of damage to the tubes 31 which border the central passage 32 between tubes. Moreover, since there is no fastener to be undone inside the vessel 20 of the steam generator, there is little or no risk that loose parts will come loose and

  be forgotten inside the tank 20.

  Although it has been described the use of fixing screws or locking screws 46 to hold in place, in its mounting position, the locking device 40, it should be understood that other types

  Mounting systems could be used if desired.

  The present invention is not limited to the exemplary embodiments

  tion which has just been described, it is on the contrary

  variants and modifications that will occur to those skilled in the art.

Claims (16)

  1. Removable device for blocking the flow of the heat exchange fluid in a central free passage (32) through the tube bundle (31) and above the tubular plate (22) of a tank (20). ) heat exchanger of a steam generator having a hand-hole (28) in alignment with the central passage (32), said device being characterized in that it comprises a locking portion (50) which can be introduced through the hand-hole (28) into the passage   central section (32) and a mounting portion (41) connected to the block portion   ge (50) and fixed in the handhole (28) in the mounted position, this locking portion (50) and this mounting portion (41) forming a one-piece assembly (40) movable between a retracted position, located completely at outside the tank (20) of the heat exchanger, and a use position in which the mounting portion (41) is in the mounted position and the locking portion (50) is oriented   in a blocking position in the cnetral passage (32) to prevent   the flow of fluid along this central passage (32).   2. Device according to claim 1, characterized in that   the locking portion (50) is integral with the mounting portion (41).   3. Device according to claim 1, characterized in that the locking portion (50) comprises a rectangular flat portion (52) disposed approximately perpendicular to the tube plate (22) and spanning the central passage (32) when this part blocking (50)   is oriented in its blocking position.   4. Device according to claim 3, characterized in that the locking portion (50) comprises an L-shaped section, having a first leg (51) connected to the mounting portion (41) and a second leg (52) consisting of the rectangular flat part and   disposed perpendicularly to the first leg (51).   5. Device according to claim 1, characterized in that no part of this device in the position of use is   extends outside the punch (28).   6. Device according to claim 1, characterized in that the locking portion (50) in its locking orientation is arranged approximately perpendicular to the tube plate (22) and is   spaced from the handhole (28) by a predetermined distance.   7. Device according to claim 1, characterized in that it further comprises a reinforcing means (53) fixing the part of   locking (50) to the mounting portion (41).   8. Device according to claim 1, characterized in that   the mounting portion (41) includes a closed inner end having   view to be disposed in the socket (28) in the mounting position and an open outer end, means for securing said mounting member (41) in the mounting position, and in that the blocking means (50) is connected to the closed inner end of the element   mounting element (41), the locking element (52) being placed in an orientation   blockage approximately perpendicular to the tubular plate (22) and substantially spanning the central passage (32) to prevent   the flow of fluid along this central passage (32).   9. Device according to claim 8, characterized in that   the mounting element (41) has an outer diameter which is only slightly   less than the inside diameter of the hand-hole (28).   Device according to Claim 8, characterized in that the mounting element (41) comprises an annular retaining ring (42) protruding radially outwardly from this mounting element and designed to fit into the vessel ( 20) of the heat exchanger to limit the insertion depth of the mounting element (41) in the punch (28).   11. Device according to claim 10, characterized in that the tank (20) has a counterbore portion (29) at the outer end of the handhole (28), the retaining ring (42).   can be housed in this counterbore portion (29).   Device according to claim 8, characterized in that the means for securing the mounting element (41) comprises a fixing screw (46) which extends radially outwardly through the mounting element (41). in order to be in contact with the   inner surface of the handhole (28).   13. Device according to claim 8, characterized in that no part of this device in the position of use is   extends outside the punch (28).   14. Device according to claim 8, characterized in that   that the mounting element (41) is integral with the locking means (50).   15. Device according to claim 14, characterized in that the locking means (50) comprises an L-shaped element comprising two perpendicular branches (51, 52), one of which (52) constitutes a locking element and of which the other (51) is integral with the mounting means (41). Device according to claim 15, characterized in that   the locking element (52) has a rectangular shape.